The recording sheet is preferably adhered along one side to the glass plate therebelow. Static electricity may, however, occur when a rubber cover in a tiltable lid has been pressed towards the adhered recording sheet and is subsequently opened. The attractive force between the cover and the recording sheet caused by the charge may become so strong that the recording sheet follows the movement of the lid when said lid is opened. In addition the operator can be subjected to electric shocks. Previous attempts to solve these problems have not been successful.